Pipe coupling between relatively hard and soft tubes



Aug. 16, 1960 E. c. HUTCHINS PIPE COUPLING BETWEEN RELATIVELY HARD AND SOFT TUBES Original Filed Aug. 18, 1954 9 o, m a v 2 l (I m V i ll 1 .1 1 l I h u" IJL II II all. I I'm Iiu x l. l 3 1 5 M 2 M O a o 2 M 3 p/ v N "II I -r|| l I I l I l !..w m L u w k 2 H mg a F United States Patent PIPE COUPLING BETWEENRELATIVELY HARD AND sorr TUBES Everett C. Hutchins, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Original application Aug. 18, 1954, Ser. No. 450,600,

now Patent No. 2,816,211, dated Dec. 10, 1957. Divided and this application Nov. 13, 1956, Ser. No. 621,845

1 Claim. (Cl. 285-173) This invention relates to refrigerating apparatus or the like and more particularly to the bonding of dissimilar metals, which are ordinarily difiicult to bond, such as aluminum, or relatively soft tubing to copper, steel, or relatively hard tubing or to fixtures used in such apparatus.

This application is a division of S.N. 450,600, filed August 18, 1954 and issued as Patent #2,816,211 on December 10, 1957.

An object of this invention is to. provide a method of bonding dissimilar metals, such as aluminum or relatively soft tubing to other tubing such as copper, steel or relatively hard tubing or to fixtures such as expansion valves, or the like, used in refrigerating apparatus or similar apparatus, by the use of a steel or relatively harder short tube within said tubing.

Another object of this invention is to provide a novel joint between dissimilar metals, such as aluminum or relatively soft tubing and copper, steel or relatively hard tubing or fixtures used in such apparatus, including a short steel or relatively harder tube within said tubing at said joint.

Another object of this invention is to provide an apparatus for bonding dissimilar metals, such as aluminum or relatively soft tubing to copper, steel or relatively hard tubing or to fixtures used in refrigerating apparatus or the like by the use of a short steel or relatively harder tube within such tubing.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

Figure 1 is a vertical cross section showing an early stage in the method of bonding the tubing.

Figures 2, 3 and 4 are figures somewhat similar to Figure 1, and showing later stages in the method.

Figure 5 is a diagrammatic representation of an apparatus for bonding the tubing.

Reference is made to aluminum, copper and steel in the following description, as illustrative and not for the puropse of limitation. Such terms are used as representative of relatively soft, relatively hard and relatively harder materials or metals.

Related subject matter is disclosed in the copending application S.N. 450,599 and now abandoned, filed August 18, 1954, and assigned to the assignee of the present invention.

This invention is particularly useful in the joining of aluminum and copper tubing for use in refrigerating apparatus or the like where tubing of different material or similar materials are to be joined, but is also useful in joining tubing and/or fixtures of any different metals, as will be apparent.

In practicing the method of joining tubing, one end Patented Aug. 16,- 1960 of an aluminum or relatively soft tube 10 is formed into an aluminum bell 11 by any suitable apparatus, now well known. A copper or relatively hard tube 12 has a first copper bell '13 formed thereon near one end, which bell 13 is of substantially the same inner dimension as that of the aluminum bell 11. A second copper bell 14 is formed at the end of the first copper bell 13. The bells 13 and 14 are formed by any well known suitable apparatus. The second copper bell 14 has an inner dimension substantially the same as the outer dimension of the aluminum bell 11. If desired, the end of hell 14 is tapered at 26 by any suitable means. A short steel or relatively harder tube 15 is placed within the bells 11 and 13, and the bell 11 is telescoped into the bell 14 as shown in Figure 1. The outer dimension of tube 15 is substantially the same as the inner dimension of bells 11 and 13. Only enough clearance is provided in said dimensions to permit the indicated telescoping action. All parts of thetubes to be welded are previously cleaned by mechanical or chemical means, now well known.

Separable dies, made of mating halves, for example, surround the tubing, and are pushed towards each other to push the tubes towards each other and cause the second copper bell 14 to bulge outwardly, as shown in Figures 2, 3 and 4, to form an inner cavity 16 and cause the aluminum bell 11 to bulge outwardly near its end into said cavity 16 as indicated at 17.

A die, made of halves 20 and 21, surrounds the bell 13 somewhat loosely and engages the shoulder 22 which joins the first and second copper bells 13 and 14. A molybdenum, or similar material, die made of halves 23 and 24 surrounds the lower part of bell 11 and is circumferentially slightly spaced therefrom, to concentrate the flow of current into hell 14. The molybdenum die is provided with a tapered shoulder 25 which is adjacent to and mates the tapered end 26 of the bell 14, as indicated in Figure l. The molybdenum die 23, 24 does not touch the aluminum tube 10 or bell 11. Another die made of halves 3t) and 31 surrounds the main body of the tube 10, if desired, adjacent the shoulder 32 where the main body of tube 10 joins bell 11. The die 30, 31 tightly grasps or pushes the tube 10 so that no relative axial movement occurs between the tube 10 and the die 30, 31. Any method may be used to move the halves of the dies toward and away from each other. For example, bolts or screws, not shown, at the ends of the halves may move the halves toward and away from each other. Instead, the die halves may be moved toward and away from each other by air or hydraulically operated plungers, not shown.

The machine 40, shown in Figure 5 has an arm 41 which carries the die 20, 21. Arm 42 carries the dies 23, 24 and 30, 31. The arms 41 and 42 are moved relatively towards and away from each other, and the machine is capable of passing a heavy momentary current through the tubing, at the selected time. The machine without the dies is now well known as an air operated press welder. Any equivalent machine may be used.

The arms 41 and 42 are moved relatively towards each other, as by maintaining the arm 42 stationary and moving the arm 41 downward. A subsequent step is indicated in Figure 2 wherein the dies have approached each other sufiiciently to bulge the bell 14 outwardly to form the inner cavity 16 and to cause the end of bell 11 to bulge outwardly into the cavity 16 as indicated at 17. The steel tube 15, which has substantially the same outer dimension as the inner dimension of the main parts of bells 11 and 13, prevents the inward flow of the bells, and thus insures the outward bulging action shown in Figure 2.

Upon the completion of the step indicated in Figure 2, the die halves 30 and 31 are separated, as shown in Figure 3, and the machine 40 sends a heavy momentary current through the die 23, 24, the bell 14, and die 20, 21. This current is sufficient to heat the tubing to a welding temperature, which causes the metal to flow and weld as indicated in Figure'3, the metal melted by the heat flowing downwardly and welding against the main body of the bell 11 as indicated at 45. The release of die halves 30, 31 permits the tube and bell 11 to move axially the necessary amount during the weld. After the current has stopped, the pressing action is continued during the cooling period to permit the weld to freeze under pressure.

Thereafter, all the dies are separated, as shown in Figure 4, and the tubing is removed from the machine in completely joined and fluid tight condition.

Tubing 10 and 12 is shown as being of the same main inner dimension, but these tubings may be of different diameter and the bells formed thereon can then have the similar mating dimensions heretofore described.

The short steel tube 15 remains in the tubing and is in the nature of a permanent mandrel used in the bonding operation.

Either tube 10 or 12 may be a part of a fixture to be used in a refrigerating apparatus or the like, if desired.

While the forms of embodiment of the invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

A joint between a relatively soft tube and a relatively hard tube, said tubes having substantially the same wall thickness, comprising: a bell at the end of said relatively soft tube; a first bell at the end of said relatively hard tube and of substantially the same inner dimension as that of said relatively soft tube bell; a second bell at the end of said first bell, said second bell being bulged outwardly to form an inner cavity and the end of said soft tube bell being bulged into said cavity; and a third tube of a hardness greater than said relatively hard tube within said bells and held against endwise displacement by the end walls of said first mentioned two bells, said third tube being of an outer dimension substantially the same as the inner dimension of said soft tube bell; and weld means joining adjacent surfaces of said relatively hard and relatively soft tubes, the end of said relatively soft tube being wedged between said relatively hard tube and said third tube.

References Cited in the file of this patent UNITED STATES PATENTS 199,180 Bricknell Jan. 15, 1879 1,044,264 Schurhoif Nov. 12, 1912 1,735,289 McClintock Nov. 12, 1929 1,738,915 Mueller Dec. 10, 1929 1,886,275 Nell Nov. 1, 1932 1,912,993 Murray July 6, 1933 1,937,239 McWane Nov. 28, 1933 1,941,115 Strenger Dec. 26, 1933 2,273,154 Stromsoe Feb. 17, 1942 2,513,365 Rogoff July 4, 1950 2,545,930 Richardson Mar. 20, 1951 2,741,498 Elliott Apr. 10, 1956 2,760,346 Grenell Aug. 28, 1956 2,787,481 Bushchow et a1. Apr. 2, 1957 FOREIGN PATENTS 145,190 Great Britain July 2, 1920 347,429 Great Britain Apr. 30, 1931 

